brands dont matter as far as stuff working together.
You can add ports to it simply by adding a 4 port or 8 port switch....I see the 4 port ones for like $20 and below all the time....you would just come from one of the ports of the router to the switch and then youd have all the extra ports on the switch. Frankly most of the switches and routers now auto select everything so you dont even have to worry if you have a crossover cable or regular cable.
If you want to add wireless then just get a wireless router and then if you need more ports you can just use the old router but just use it as a glorified switch. In other words use the wireless router to actually hook to the cable modem...then out of one of the ports of the wireless router you would come to one of the "Lan" ports of the second router...basically, as I said, you would just be using it as a switch. You wouldnt use the "wan" input of the second router at all.
(just in case you didnt know, a switch is just a smarter version of a hub..so a hub would actually work, but a switch is technically better because it keeps the info from "colliding"..therefore keeping the speeds up etc...switches used to cost a ton more than hubs but now they are so cheap that it would be pointless to buy a hub)
JP